Testing for Radon in Real Estate Transactions

Radon testing is not required by law or regulated in Wisconsin. We  recommend that individuals certified in a Radon Proficiency Program for Residential Measurement be used for real estate transfers. We maintain a list of individuals who are certified by the American Association of Radon Scientists and Technologists, or the National Radon Safety Board.

For real estate transactions, radon testing is often done in basements. However, the year average radon on the main floors of houses in  Wisconsin typically averages half of the basement, two-day, closed-house measurements. And the lung cancer risk from radon depends on exposure of the residents in the spaces they actually spend their time. A year-long measurement averages seasonal variations and times when the house is open, giving a more accurate estimate of exposure and lung cancer risks.

The following highlights are from the guidance for radon testing in real estate transactions, given in the US EPA's November 2006 publication, Home Buyer's and Seller's Guide to Radon.

  • Use two passive radon detectors simultaneously, four inches apart, or two sequentially, or one electronic radon monitor recording fresh data every hour.
  • The minimum measurement duration is 48 hours.
  • Maintain closed-house conditions on all floors during the test, and for 12 hours before it if the test lasts less than four days.
  •  Do not conduct tests lasting less than four days during severe storms or periods of high winds
  • Use tamper protection for the radon detectors and windows.
  • Test location: the lowest level of the home that is suitable for occupancy without renovations. In a room that will be frequently occupied.  "EPA recommends that testing device(s) be placed in the lowest level of the home that could be used regularly, whether it is finished or unfinished. ."  
  • Not in a bathroom, kitchen or laundry room. At least 20" above the floor, away from windows, doors, outside walls, heat sources, humidity and breezes.
  •  The U.S. EPA Home Buyer's and Seller's Guide to Radon says (on page 6): "You should test in the lowest level of the home which is suitable for occupancy and finished. … that a buyer could use for living space without renovations."

Radon Mitigation System Checklist

For buyers of homes already having radon control systems in them, and for home buyers to verify the components of a proposed radon control system, a checklist (PDF, 43 KB) has been developed by the American Society of Home Inspectors in conjunction with the U.S. EPA. Please see the second page of this checklist.

Last Revised: August 6, 2015